This invention relates generally to injection molding and more particularly to a sprue gated injection molding system having nozzles with an easily removable gate insert.
Gate inserts or nozzle seals are well known in the art. Early examples for use in valve gated systems are shown in U.S. Pat. No. 4,043,740 to Gellert which issued Aug. 23, 1977 and U.S. Pat. No. 4,286,941 to Gellert which issued Sept. 1, 1981. More recent examples of threaded gate inserts are shown in Gellert's Canadian patent applications serial numbers 532,677 filed Mar. 20, 1987 entitled "Injection Molding Nozzle and Method", 559,000 filed Feb. 16, 1988 entitled "Injection Molding Heated Gate Insert and Method" and the applicant's Canadian patent application serial number 549,516 filed Oct. 16, 1987 entitled "Injection Molding System Having Clamped Rotatable Nozzles and Method". Gate inserts in combination with heat conductive torpedoes are also known as shown in U.S. Pat. No. 4,279,588 to Gellert which issued July 21, 1981, U.S. Pat. No. 4,266,723 to Osuna-Diaz which issued May 12, 1981, U.S. Pat. No. 4,450,999 to Gellert which issued May 29, 1984 and the applicant's Canadian patent application serial number 529,897 filed Feb. 17, 1987 entitled "Injection Molding System having Manifold with Side Mounted Nozzles and Method". While these previous gate inserts function very well for many applications, the continual development of difficult to mold materials has made heat transfer in the area of the gate even more critical to successful operation of the system. More specifically, it is very desirable in this situation that there be optimum uniform heat flow between the gate insert and the surrounding cooled mold. While the area of surface contact between them can be varied somewhat by the moldmaker depending upon the application, this is not sufficient if there is not good contact between them. Non-uniform contact between them prevents the system being designed to accurately provide the correct amount of cooling for the particular application. Furthermore, due to deterioration of the gate insert as a result of corrosion and abrasion it is desirable that it be easily removable. Bearing contact between a resilient forward portion of the gate insert and the surrounding mold provides improved more uniform conductivity between them while providing a removal flange facilitates removal of the gate insert simplifies manufacture of the gate insert.